Deep-sky objects Sagittarius (constellation)

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the omega nebula, known horseshoe or swan nebula.


the milky way @ densest near sagittarius, galactic center lies. result, sagittarius contains many star clusters , nebulae.


nebulae

sagittarius contains several well-known nebulae, including lagoon nebula (messier 8), near λ sagittarii; omega nebula (messier 17), known horseshoe nebula or swan nebula, near border scutum; , trifid nebula (messier 20), large nebula containing young, hot stars.



the lagoon nebula (m8) emission nebula located 5,000 light-years earth , measures 140 light-years 60 light-years (1.5°). though appears grey in telescopes unaided eye, long-exposure photographs reveal pink hue, common emission nebulae. bright, integrated magnitude of 3.0. lagoon nebula discovered independently john flamsteed in 1680, guillaume le gentil in 1747, , charles messier in 1764. central area of lagoon nebula known hourglass nebula, named distinctive shape. hourglass nebula has shape because of matter propelled herschel 36. lagoon nebula features 3 dark nebulae catalogued in barnard s catalog. lagoon nebula instrumental in discovery of bok globules, bart bok studied prints of nebula intensively in 1947. approximately 17,000 bok globules discovered in nebula 9 years later part of palomar sky survey; studies later showed bok s hypothesis globules held protostars correct.
the omega nebula bright nebula; has integrated magnitude of 6.0 , 4890 light-years earth. discovered in 1746 philippe loys de chésaux; observers since him have differed in how view nebula, hence myriad of names. viewed checkmark, seen swan george f. chambers in 1889, loon roy bishop, , curl of smoke camille flammarion.
the trifid nebula (m20, ngc 6514) emission nebula in sagittarius lies less 2 degrees lagoon nebula. discovered french comet-hunter charles messier, located between 2,000 , 9,000 light-years earth , has diameter of approximately 50 light-years. outside of trifid nebula bluish reflection nebula; interior pink 2 dark bands divide 3 areas, called lobes . hydrogen in nebula ionized, creating characteristic color, central triple star, formed in intersection of 2 dark bands. m20 associated cluster has magnitude of 6.3.
the red spider nebula (ngc 6537) planetary nebula located @ distance of 4000 light-years earth.
ngc 6559 star forming region located @ distance of 5000 light-years earth, in constellation of sagittarius, showing both emission (red) , reflection (bluish) regions.

the grouping of lagoon nebula, trifid nebula, , ngc 6559 called sagittarius triplet.


in addition, several other nebulae have been located within sagittarius , of interest astronomers.



m24, called small sagittarius star cloud, star cluster approximate magnitude of 3. 9400 light-years away, has diameter of approximately 330 light-years. embedded in m24 ngc 6603, smaller star cluster dense. ngc 6567, dim planetary nebula, , barnard 92, bok globule, nearby.
ngc 6445 planetary nebula approximate magnitude of 11. large nebula @ on 1 arcminute in diameter, appears close globular cluster ngc 6440.
ngc 6638 dimmer globular @ magnitude 9.2, though more distant m71 @ distance of 26,000 light-years. shapley class vi cluster; classification means has intermediate concentration @ core. approximately degree away brighter globulars m22 , m28; ngc 6638 southeast , southwest of clusters respectively.

other deep sky objects

messier 54 first globular cluster found outside milky way.


in 1999 violent outburst @ v4641 sgr thought have revealed location of closest known black hole earth, later investigation increased estimated distance factor of 15. complex radio source sagittarius in sagittarius, near western boundary ophiuchus. astronomers believe 1 of components, known sagittarius a*, associated supermassive black hole @ center of galaxy, mass of 2.6 million solar masses. sagittarius dwarf elliptical galaxy located outside milky way.


baade s window area little obscuring dust shows objects closer milky way s center visible. ngc 6522, magnitude 8.6, , ngc 6528, magnitude 9.5, both globular clusters visible through baade s window. 20,000 , 24,000 light-years earth, shapley classes of vi , v respectively, both moderately concentrated @ cores. ngc 6528 closer galactic core @ approximate distance of 2,000 light-years.


2mass-gc02, known hurt 2, globular cluster @ distance of 16 thousand light-years earth. discovered in 2000 joselino vasquez, , confirmed team of astronomers under leadership of r. j. hurt @ 2mass.








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